0:00:03 > 0:00:071,000 years ago, one of the world's greatest civilisations
0:00:07 > 0:00:11built an empire here in Cambodia.
0:00:14 > 0:00:18It dominated Southeast Asia for nearly 600 years...
0:00:20 > 0:00:23..and was the biggest superpower the region has ever seen.
0:00:25 > 0:00:28Their capital was the great city of Angkor.
0:00:29 > 0:00:31This was an extensive kingdom.
0:00:31 > 0:00:34Its power surpassed the modern-day borders,
0:00:34 > 0:00:38an empire this great is something to be truly marvelled at
0:00:38 > 0:00:41and to have so much remaining from that time,
0:00:41 > 0:00:44it's just a remarkable thing to witness.
0:00:46 > 0:00:48Starting as a nation of rice farmers,
0:00:48 > 0:00:51the Khmer people would go on to build some of the most
0:00:51 > 0:00:54spectacular structures of the Medieval age.
0:00:56 > 0:01:01The pinnacle of their culture was the great temple Angkor Wat,
0:01:01 > 0:01:06still the largest religious monument in the world.
0:01:06 > 0:01:11But 500 years ago, the Khmer kings abandoned their capital.
0:01:11 > 0:01:15The city of Angkor was quickly devoured by the jungle.
0:01:15 > 0:01:21For over 100 years, scientists have been unable to explain why
0:01:21 > 0:01:25one of the world's most powerful civilisations abandoned their city.
0:01:27 > 0:01:30Now an international team of experts is trying to solve
0:01:30 > 0:01:34one of the great mysteries of the Medieval age.
0:01:34 > 0:01:37As archaeologists, we're interested in questions of, who the
0:01:37 > 0:01:38people were who built these temples,
0:01:38 > 0:01:41where do they come from? How did they survive?
0:01:41 > 0:01:44What did their cities look like and what happened to them?
0:01:44 > 0:01:48Using a revolutionary laser-scanning technique called LIDAR,
0:01:48 > 0:01:52they're looking beneath the jungle to uncover the secrets of this
0:01:52 > 0:01:55extraordinary civilisation.
0:01:55 > 0:02:00This is the royal palace, the civil centre of that ancient city
0:02:00 > 0:02:02where the king would live.
0:02:02 > 0:02:05It's amazing. Really amazing.
0:02:07 > 0:02:11For the first time in 500 years, LIDAR is helping to reveal
0:02:11 > 0:02:15the lost metropolis of the people who built Angkor Wat.
0:02:15 > 0:02:18Some colleagues of mine have described it as, essentially,
0:02:18 > 0:02:20a scientific revolution.
0:02:20 > 0:02:24We are now closer than ever before to
0:02:24 > 0:02:27an understanding of how the Khmer people came to dominate
0:02:27 > 0:02:33Southeast Asia and why their great city ultimately collapsed.
0:02:58 > 0:03:01Deep inside the stone chambers of Angkor Wat,
0:03:01 > 0:03:03the annual candle ceremony - Meak Bochea.
0:03:09 > 0:03:12A Buddhist ceremony to purify the mind.
0:03:12 > 0:03:15Many people think of Angkor Wat as a dead monument,
0:03:15 > 0:03:17a place that was abandoned
0:03:17 > 0:03:21and the tourists come here just to admire its architecture.
0:03:21 > 0:03:23But, you know, it's a living monument.
0:03:26 > 0:03:31It's a place which has real life in amongst the people of Cambodia.
0:03:36 > 0:03:38It's an amazing place, a special place.
0:03:40 > 0:03:43Angkor Wat is a place full of surprises.
0:03:50 > 0:03:54Angkor Wat is one of the most beautiful and mysterious buildings
0:03:54 > 0:03:56in the world.
0:03:59 > 0:04:03Five huge towers shaped like lotus buds,
0:04:03 > 0:04:06surrounded by a six-kilometre moat.
0:04:09 > 0:04:12A temple of perfect symmetry covering an area
0:04:12 > 0:04:15of two square kilometres.
0:04:15 > 0:04:19This is one of the wonders of the Medieval world.
0:04:19 > 0:04:23What I feel when I see Angkor Wat is, I am impressed
0:04:23 > 0:04:25by the coming together,
0:04:25 > 0:04:29the collectivity of a great many kinds of genius here.
0:04:29 > 0:04:31The genius of the mathematician,
0:04:31 > 0:04:34the genius of the artist, the genius of the architect,
0:04:34 > 0:04:37the genius of the engineer and the genius of the people who
0:04:37 > 0:04:39aspired to build these things.
0:04:39 > 0:04:41Who cannot be in love with Angkor?
0:04:43 > 0:04:46The temple was constructed nearly 1,000 years ago.
0:04:47 > 0:04:49In Europe at that time,
0:04:49 > 0:04:52the Normans would spend over 100 years building their
0:04:52 > 0:04:54vast cathedrals.
0:04:54 > 0:04:59The Khmer people completed Angkor Wat in under 40,
0:04:59 > 0:05:04and that included 2km of intricate engravings with
0:05:04 > 0:05:08nearly 2,000 celestial dancers from Hindu mythology,
0:05:08 > 0:05:11every one unique.
0:05:13 > 0:05:16In the 12th century, this was the spiritual and administrative
0:05:16 > 0:05:18heart of the city of Angkor.
0:05:18 > 0:05:21It would come to rule an empire
0:05:21 > 0:05:25that stretched a million square kilometres across Southeast Asia.
0:05:33 > 0:05:36Every year, more than two million people are drawn to the Khmer's
0:05:36 > 0:05:39archaeological treasures.
0:05:39 > 0:05:44They drive a tourist industry worth more than 2 billion a year,
0:05:44 > 0:05:48nearly 20% of Cambodia's entire economy.
0:05:50 > 0:05:53But the people who built this temple
0:05:53 > 0:05:57and the city around it remain an enigma.
0:05:57 > 0:06:01Most evidence for how the Khmer people built their city
0:06:01 > 0:06:04has been lost or swallowed by the jungle.
0:06:04 > 0:06:08Archaeologists and historians have been studying Angkor
0:06:08 > 0:06:11for about 150, 160 years, but little was known
0:06:11 > 0:06:14about the actual people who inhabited these spaces.
0:06:14 > 0:06:17The great stone buildings were one thing,
0:06:17 > 0:06:19but not everyone lived in the temples,
0:06:19 > 0:06:22and so more and more throughout the 20th century
0:06:22 > 0:06:25the questions were being asked, what about the everyday people?
0:06:25 > 0:06:28Who were they? Where did they live? What was their life like?
0:06:32 > 0:06:37Now a new project is attempting to solve some of these mysteries...
0:06:39 > 0:06:42..by using a revolutionary technology called LIDAR.
0:06:44 > 0:06:47We're airborne above Angkor.
0:06:47 > 0:06:51Damian Evans, from the University of Sydney, is leading a team
0:06:51 > 0:06:55of international experts who are peeling back the layers of forest
0:06:55 > 0:06:59to reveal the secrets of the people who built Angkor Wat.
0:07:03 > 0:07:06Most of the city that existed here 1,000 years ago
0:07:06 > 0:07:10would have been made of very, very flimsy material.
0:07:10 > 0:07:14Just light pieces of wood and thatch and so on.
0:07:14 > 0:07:17Within one or two years, that stuff just rots away completely.
0:07:17 > 0:07:21We can still make out these very, very subtle traces of where
0:07:21 > 0:07:26they used to be, by analysing the surface topography of the landscape.
0:07:26 > 0:07:30LIDAR works in a similar way to radar.
0:07:30 > 0:07:34It scans the ground by sending out a million laser points
0:07:34 > 0:07:39every four seconds and analysing the information reflected back.
0:07:40 > 0:07:44The time it takes for each pulse to break through the trees,
0:07:44 > 0:07:47hit the ground and return is measured.
0:07:47 > 0:07:49The results are then mapped.
0:07:49 > 0:07:53The shapes revealed are the footprints of structures
0:07:53 > 0:07:57from the long-lost capital of the Angkorian empire.
0:07:57 > 0:08:00We get this data back to the office, we can click a button,
0:08:00 > 0:08:05strip those trees from the picture and really, for the first time,
0:08:05 > 0:08:08see those cities of Angkor emerge in incredible detail
0:08:08 > 0:08:12on the computer screen in front of us.
0:08:12 > 0:08:15The jungle is removed in an instant.
0:08:17 > 0:08:21The LIDAR data renders an outline of everything on the surface
0:08:21 > 0:08:22of the land.
0:08:23 > 0:08:28The glory of Angkor Wat becomes a ghostly outline of digital points.
0:08:30 > 0:08:36But LIDAR also reveals the shape of the old city.
0:08:41 > 0:08:44Angkor Wat is shown to be surrounded by the ghostly
0:08:44 > 0:08:46outline of a vast metropolis.
0:08:48 > 0:08:52And we can use this data to re-build the city of Angkor
0:08:52 > 0:08:54as it would have looked over 900 years ago.
0:09:04 > 0:09:07Shadowy lines that were once roads...
0:09:10 > 0:09:14..canals long since swallowed by the jungle...
0:09:23 > 0:09:27..and the outline of thousands of houses, monasteries and palaces.
0:09:34 > 0:09:38It's an incredible leap forward for us to be able to use this technique.
0:09:38 > 0:09:41You can imagine that doing things by hand on the ground
0:09:41 > 0:09:44is a process that would take decades, basically.
0:09:44 > 0:09:47Now, using these new techniques, we have the opportunity
0:09:47 > 0:09:52to do a bit of flying, just a few hours, to take that data back to the
0:09:52 > 0:09:55office and with a few clicks of the button, we see entire urban
0:09:55 > 0:09:59landscapes unfolding on the screen in front of us for the first time.
0:10:03 > 0:10:06The LIDAR imagery shows that central Angkor
0:10:06 > 0:10:09was organised into regular-sized city blocks...
0:10:10 > 0:10:14..and that many of the dwellings of the Angkorian era
0:10:14 > 0:10:17were clustered around thousands of ponds.
0:10:19 > 0:10:21LIDAR is an incredibly valuable tool,
0:10:21 > 0:10:25because what it allows us to do is to breathe life back into that landscape.
0:10:25 > 0:10:29For the first time, it reveals with exceptional clarity
0:10:29 > 0:10:32these vanished cities that surrounded the monuments
0:10:32 > 0:10:36and allows us to create a new image of Angkor as a place
0:10:36 > 0:10:39that was teeming with life and full of activity.
0:10:45 > 0:10:47LIDAR confirms that the city
0:10:47 > 0:10:51spanned an area larger than the whole of New York City.
0:10:51 > 0:10:55In the 12th century, when Angkor Wat was being built,
0:10:55 > 0:10:58London had a population of 18,000.
0:11:00 > 0:11:03It's been estimated that Angkor had a population
0:11:03 > 0:11:06approaching three-quarters of a million.
0:11:07 > 0:11:09Until the 19th century,
0:11:09 > 0:11:14Angkor was the most extensive city in the world.
0:11:19 > 0:11:22Bringing the old capital back to life
0:11:22 > 0:11:24was only one of the project's ambitions.
0:11:24 > 0:11:28LIDAR has also started giving revolutionary insights
0:11:28 > 0:11:31into the origins of the Khmer Empire.
0:11:38 > 0:11:43Since 1999, French archaeologist Jean-Baptiste Chevance
0:11:43 > 0:11:49has been studying the Kulen Hills, 40km north of Angkor.
0:11:49 > 0:11:52He has dedicated his life to uncovering
0:11:52 > 0:11:55the remains of a 9th-century Khmer settlement.
0:11:55 > 0:11:58It's a tough, simple existence.
0:11:59 > 0:12:03I've been driving around for years, so I know the place pretty well.
0:12:03 > 0:12:05I feel comfortable with the local people,
0:12:05 > 0:12:07with the research, with the temples.
0:12:07 > 0:12:09It's part of my life.
0:12:12 > 0:12:16The dirt bike is fun, it's the easiest way to go from A to B,
0:12:16 > 0:12:20especially in rainy season. Roads are turning into rivers, so you have to be cautious.
0:12:36 > 0:12:39Historians believe that the Khmer Empire
0:12:39 > 0:12:42began here in the Kulen Hills
0:12:42 > 0:12:45300 years before Angkor Wat was built.
0:12:51 > 0:12:53Before the LIDAR project,
0:12:53 > 0:12:56Jean-Baptiste used conventional archaeology
0:12:56 > 0:13:00to piece together a picture of an early Khmer capital.
0:13:02 > 0:13:04This is Rong Chen temple.
0:13:09 > 0:13:14Rong Chen sits on one of the highest peaks in the Kulen Hills.
0:13:14 > 0:13:16At the time it was being built,
0:13:16 > 0:13:21Anglo-Saxon Britain was being attacked by the Vikings.
0:13:21 > 0:13:25Rong Chen is the only mountain temple in Phnom Kulen.
0:13:26 > 0:13:29A temple made of different levels, like a pyramid,
0:13:29 > 0:13:33it has always been considered the centre of the religious city.
0:13:35 > 0:13:38Nobody has really studied and maintained this temple,
0:13:38 > 0:13:42because Angkor was attracting most of the attention.
0:13:43 > 0:13:47Inscriptions in temples built 200 years later
0:13:47 > 0:13:50suggest that Rong Chen was the religious heart
0:13:50 > 0:13:53of a new capital called Mahendrapravata.
0:13:55 > 0:14:00And it was built for a powerful Khmer king, Jayavarman II.
0:14:02 > 0:14:09Before his rule, Cambodia was a collection of small kingdoms ruled by local lords.
0:14:11 > 0:14:1411th-century inscriptions suggest that Jayavarman
0:14:14 > 0:14:17came to dominate the area by declaring himself
0:14:17 > 0:14:21to be a special mediator between God and man.
0:14:23 > 0:14:27Jayavarman II was the first king to unify those kingdoms.
0:14:27 > 0:14:31He also installed a new cult of the god-king,
0:14:31 > 0:14:33which made him even more powerful.
0:14:33 > 0:14:39That cult was perpetrated by all the kings that were following him
0:14:39 > 0:14:41and therefore Jayavarman II
0:14:41 > 0:14:45has always been referred as the king who was unifying the Khmer kingdom
0:14:45 > 0:14:49and starting the Angkorian period leading to Angkor Wat.
0:14:52 > 0:14:55With only a few ruins and inscriptions to go on,
0:14:55 > 0:15:00understanding the early days of the Khmer Empire has always been difficult,
0:15:00 > 0:15:06and for many years, archaeological digs here were also impossible.
0:15:10 > 0:15:17From 1975 to 1979, the Communist Party of Cambodia, the Khmer Rouge,
0:15:17 > 0:15:22established a totalitarian state based on the teachings of Mao Tse Tung.
0:15:24 > 0:15:27Under the leadership of dictator Pol Pot,
0:15:27 > 0:15:28they ruled by terror,
0:15:28 > 0:15:35rejecting urban culture and trying to build a self-sufficient agricultural society.
0:15:37 > 0:15:39By the end of Pol Pot's rule
0:15:39 > 0:15:43more than a million-and-a-half Cambodians had been killed.
0:15:43 > 0:15:47Many more were left with permanent injuries.
0:15:47 > 0:15:52The Kulen Hills was one of the last strongholds of the Khmer Rouge.
0:15:53 > 0:15:56Until '96, it was completely impossible to come here.
0:15:56 > 0:16:02At that time, the Khmer Rouge were occupying an artillery battery just behind this temple.
0:16:02 > 0:16:06As a Westerner, you would've been kidnapped or killed.
0:16:06 > 0:16:09Even the Cambodians couldn't come here, it would have been just too dangerous.
0:16:11 > 0:16:15Today, the Kulen Hills remain heavily mined.
0:16:18 > 0:16:22So this part of the Khmer Empire is one of the least explored.
0:16:24 > 0:16:30Jean-Baptiste's work and his participation in the LIDAR project is changing that.
0:16:30 > 0:16:34Laser information reflected from the surface of the Kulen Hills
0:16:34 > 0:16:37revealed the shadow of Jayavarman's city
0:16:37 > 0:16:40for the first time in more than 1,000 years.
0:16:42 > 0:16:45The LIDAR results showed that Mahendrapravata
0:16:45 > 0:16:50was a much more sophisticated city than anyone had expected.
0:16:50 > 0:16:53It also covered a much greater area.
0:16:53 > 0:16:56We found the urban network, which is massive,
0:16:56 > 0:17:00which is covering at least 8km by 4km,
0:17:00 > 0:17:03what you have here is the area which was covered by the LIDAR.
0:17:03 > 0:17:08It's very, very surprising, because we passed over those sites for years.
0:17:08 > 0:17:12This is a modern road we use almost every day,
0:17:12 > 0:17:14but you go in the field and you barely see things.
0:17:14 > 0:17:17We knew that in Kulen Hills you had a high concentration of temples,
0:17:17 > 0:17:20one of them being the mountain temple,
0:17:20 > 0:17:24but we didn't really know how it was connected together.
0:17:24 > 0:17:28We didn't have the link between all these religious sites.
0:17:28 > 0:17:32The LIDAR give us a complete vision, but in a way that is so spectacular
0:17:32 > 0:17:34that we couldn't really believe it.
0:17:34 > 0:17:38When we saw the result, that was like a big surprise, to be honest.
0:17:43 > 0:17:47The LIDAR survey provides precise information
0:17:47 > 0:17:52about where to look for the remains of further hidden structures.
0:17:52 > 0:17:56This is a GPS, which allows me to know exactly where I am.
0:17:56 > 0:17:59And we have downloaded the LIDAR result on it,
0:17:59 > 0:18:02so I know exactly where I am, according to the LIDAR.
0:18:02 > 0:18:04And I can check every feature,
0:18:04 > 0:18:07I can check everything going back on the field.
0:18:09 > 0:18:11In an area cleared of mines,
0:18:11 > 0:18:14Jean-Baptiste is following up LIDAR data
0:18:14 > 0:18:18that suggests the presence of an unexpected structure.
0:18:31 > 0:18:33This is what I was looking for.
0:18:33 > 0:18:37We have, actually, here two termites.
0:18:37 > 0:18:39One here and one over there.
0:18:39 > 0:18:42They're all in a line and this is not natural.
0:18:44 > 0:18:47Termites don't build their mounds in straight lines in nature,
0:18:47 > 0:18:50yet here there are six of them.
0:18:51 > 0:18:55The LIDAR map suggests that the termites built their nests
0:18:55 > 0:18:59on the remains of an earth bank built in the 9th century
0:18:59 > 0:19:01at the edge of a medieval Khmer road.
0:19:02 > 0:19:05So we're standing exactly on the blue arrow here.
0:19:05 > 0:19:10What we have beneath is the LIDAR images
0:19:10 > 0:19:13and on the top, we have highlighted the main road.
0:19:13 > 0:19:18So if you go this way, you will see that line that we have on the screen here,
0:19:18 > 0:19:22and this is exactly the bank of that massive road.
0:19:24 > 0:19:29The termites are unwitting markers of a vast boulevard...
0:19:30 > 0:19:33..80m wide, 6km long.
0:19:35 > 0:19:38The size of these roads are amazing.
0:19:38 > 0:19:40You could have a plane landing here,
0:19:40 > 0:19:43you could have dozens of elephant running,
0:19:43 > 0:19:46and probably hundreds if not thousands of people.
0:19:47 > 0:19:50It would have been a very impressive sight.
0:19:52 > 0:19:55The LIDAR images of Mahendrapravata
0:19:55 > 0:20:00reveal that Jayavarman II began the construction of a remarkable city.
0:20:00 > 0:20:05The Khmer people managed to clear tens of kilometres of jungle
0:20:05 > 0:20:09to begin the construction of their new capital.
0:20:12 > 0:20:17The LIDAR survey reveals a huge centrally planned metropolis -
0:20:17 > 0:20:19canals,
0:20:19 > 0:20:22reservoirs,
0:20:22 > 0:20:24dams
0:20:24 > 0:20:27and a network of giant boulevards
0:20:27 > 0:20:31covering an area of at least 30 square kilometres.
0:20:56 > 0:20:58We're actually here on a dam,
0:20:58 > 0:21:01which is a massive dyke blocking the valley,
0:21:01 > 0:21:04one of the main valleys of the Kulen Hills,
0:21:04 > 0:21:06and it's running over 300 metres
0:21:06 > 0:21:10and blocking right behind me a huge reservoir.
0:21:10 > 0:21:14It's covered now by vegetation, it's a big swamp,
0:21:14 > 0:21:17but at that time you have to imagine water all over.
0:21:21 > 0:21:25LIDAR allows us to re-imagine this early Khmer city.
0:21:32 > 0:21:35A huge reservoir of eight square kilometres
0:21:35 > 0:21:39to sustain a rapidly growing population.
0:21:46 > 0:21:50In a sense you could say that LIDAR is literally and figuratively
0:21:50 > 0:21:54shining a light into these forgotten aspects of Khmer history.
0:21:54 > 0:21:58The focus has always been on the temples and the monuments
0:21:58 > 0:22:01and these elite aspects of Khmer civilisation.
0:22:01 > 0:22:04For the first time we can consider the bigger picture
0:22:04 > 0:22:09and put people back and consider these cities in all of their complexity.
0:22:09 > 0:22:12Constructions like the dam
0:22:12 > 0:22:15show that the city was ruled by a leader
0:22:15 > 0:22:19who could plan and deliver huge engineering projects.
0:22:19 > 0:22:20BIRDSONG
0:22:22 > 0:22:24You have a massive structure
0:22:24 > 0:22:27irrigating and controlling the water system up here.
0:22:27 > 0:22:30This required a huge amount of labour,
0:22:30 > 0:22:34therefore whoever is behind this is quite strong in terms of power,
0:22:34 > 0:22:36in terms of politics.
0:22:41 > 0:22:45A powerful political system was also needed to help overcome
0:22:45 > 0:22:48one of the Khmer people's major challenges.
0:22:48 > 0:22:51THUNDER RUMBLES
0:23:03 > 0:23:06A metre-and-a-half of rain falls in the monsoon
0:23:06 > 0:23:11between May and November, nearly 90% of the annual total,
0:23:11 > 0:23:17and then, after six months of deluge, the long dry season begins.
0:23:17 > 0:23:24Temperatures hover around 40 Celsius and for six months nothing grows.
0:23:24 > 0:23:29If the crops fail during the wet season...famine follows.
0:23:36 > 0:23:39The Khmer were obsessed with water
0:23:39 > 0:23:42and at this river in the Kulen Hills,
0:23:42 > 0:23:44they sought to sanctify it
0:23:44 > 0:23:49by creating an elaborate underwater shrine.
0:23:50 > 0:23:53These carvings in the rock of the river bed
0:23:53 > 0:23:55were made in the 11th century,
0:23:55 > 0:23:59200 years after Jayavarman founded his capital.
0:23:59 > 0:24:04The shapes represent Hindu symbols of male and female fertility.
0:24:06 > 0:24:10This is one of my favourite places here because it's beautiful.
0:24:10 > 0:24:13It's a river bed which is completely carved for more than 1km,
0:24:13 > 0:24:17carved with this symbol of the Khmer and the Indian mythologies.
0:24:17 > 0:24:19This is a very unique place.
0:24:24 > 0:24:29These intricate designs were carved to preserve life.
0:24:35 > 0:24:38The water running here goes to the Angkor region.
0:24:38 > 0:24:44This sacred carving brings a kind of spiritual value to the water
0:24:44 > 0:24:47going down to the reservoir and to the rice crops.
0:24:47 > 0:24:49The whole idea is quite magical.
0:24:53 > 0:24:58Rainwater from the Kulen Hills flows over these carvings
0:24:58 > 0:25:00down to the Cambodian plains.
0:25:18 > 0:25:25The sanctified water sustained the staple of life for an entire people.
0:25:32 > 0:25:3790 years after Jayavarman made Mahendrapravata a capital of his kingdom,
0:25:37 > 0:25:41the administration moved here to Angkor.
0:25:45 > 0:25:48Landscape archaeologist Scott Hawken
0:25:48 > 0:25:52has been studying how rice farming shaped the new capital.
0:25:54 > 0:25:57Mostly for the history of research on Angkor,
0:25:57 > 0:26:02people have been studying temples, and the magnificent structures
0:26:02 > 0:26:04that everybody talks about and notices,
0:26:04 > 0:26:08but you can't understand the city until you go to the rice fields.
0:26:08 > 0:26:10It's really interesting to start off
0:26:10 > 0:26:14with the smallest elements of the archaeological landscape,
0:26:14 > 0:26:16the humble rice fields,
0:26:16 > 0:26:20and then to build up a picture of this mighty, mighty city
0:26:20 > 0:26:24that was over 1,000 square kilometres in size.
0:26:29 > 0:26:34The rice harvest here has always depended on a secure water supply.
0:26:44 > 0:26:47I use satellite imagery, aerial photography
0:26:47 > 0:26:49and map the rice fields
0:26:49 > 0:26:53and the particular patterns that they make within the landscape,
0:26:53 > 0:26:55then I can understand from these patterns
0:26:55 > 0:26:58how the city developed over time.
0:27:05 > 0:27:08THEY SPEAKS VIETNAMESE
0:27:12 > 0:27:15He's been farming these rice fields here for many years,
0:27:15 > 0:27:19and all this water comes from a local reservoir just upstream
0:27:19 > 0:27:22which is 1,000 years old. So it's remarkable.
0:27:22 > 0:27:25These rice fields have been watered by a reservoir
0:27:25 > 0:27:28that his ancestor built 1,000 years ago.
0:27:30 > 0:27:35Scott's work shows that the solutions found by Angkorian engineers
0:27:35 > 0:27:37are still used today.
0:27:37 > 0:27:43A successful harvest still depends on careful management of the monsoon waters.
0:27:49 > 0:27:50Rice is a very demanding crop,
0:27:50 > 0:27:54you really have to control water in a very precise way,
0:27:54 > 0:27:57and this takes a lot of labour and energy,
0:27:57 > 0:28:00and if you don't do this then the rice crops will fail.
0:28:01 > 0:28:06At first, the people of Angkor tried to reduce the chance of failure
0:28:06 > 0:28:10by building their city close to an enormous natural body of water.
0:28:12 > 0:28:16Every year, these fields are nourished by the rising waters
0:28:16 > 0:28:18of the largest lake in Southeast Asia.
0:28:20 > 0:28:23Tonle Sap...the "Great Lake".
0:28:30 > 0:28:37Tonle Sap is still critical to the survival of nearly a quarter of all Cambodians today.
0:28:37 > 0:28:40It's only when you get down and are on the lake itself
0:28:40 > 0:28:43that you really understand how vast it is.
0:28:44 > 0:28:47It's just enormous. It's like an inland sea.
0:28:56 > 0:28:58Even in the dry season, the lake covers
0:28:58 > 0:29:02nearly 2% of the surface area of Cambodia.
0:29:02 > 0:29:05During the monsoon it expands to cover
0:29:05 > 0:29:09almost 10% of the whole country.
0:29:10 > 0:29:14The edge of the Tonle Sap is a tremendously fertile resource
0:29:14 > 0:29:16for around a million people.
0:29:16 > 0:29:19As the lake swells and then as it shrinks,
0:29:19 > 0:29:21it leaves this rich layer of silt.
0:29:23 > 0:29:28But the people here had little control over the dramatic extremes
0:29:28 > 0:29:30that Tonle Sap imposed on their lives.
0:29:32 > 0:29:36During every monsoon the water rises by ten metres.
0:29:40 > 0:29:42People living here today
0:29:42 > 0:29:45are still forced to adapt to the lake's natural cycle.
0:29:51 > 0:29:54So this fascinating village here, Kompong Phluk,
0:29:54 > 0:29:58is perched up in the air on these enormous stilts,
0:29:58 > 0:30:01ten metres high in the sky.
0:30:01 > 0:30:05And this tells us something very interesting about the local environment.
0:30:05 > 0:30:08In the wet season the waters here rise up,
0:30:08 > 0:30:11so this village in the air becomes a village in amongst the water.
0:30:13 > 0:30:16It's a remarkable village, it's really surreal, it's extraordinary.
0:30:19 > 0:30:24People in the Angkorian era faced the same challenges.
0:30:24 > 0:30:26There are two ways that a society can face
0:30:26 > 0:30:32these dramatic climatic conditions of rising and falling water levels.
0:30:32 > 0:30:35It can adapt like this village has
0:30:35 > 0:30:40or it can actually take control and go beyond living on the margins
0:30:40 > 0:30:43and really try to change the ecosystems and the environment
0:30:43 > 0:30:45to suit the society itself.
0:30:47 > 0:30:52The people of medieval Angkor chose to take on the environment
0:30:52 > 0:30:57and to move from managed subsistence to a mastery of the landscape.
0:30:59 > 0:31:02If you're a subsistence farmer it's a very precarious existence,
0:31:02 > 0:31:06so the key really to surviving in this kind of landscape
0:31:06 > 0:31:10is to develop technologies to overcome that inherent limitation.
0:31:13 > 0:31:18The people of Angkor developed new engineering skills.
0:31:19 > 0:31:21And nearly 1,000 years ago,
0:31:21 > 0:31:25they built two huge reservoirs known as "barays".
0:31:26 > 0:31:32Right now, just below us is the West Baray, the largest of the reservoirs of the Angkor period.
0:31:32 > 0:31:34It's an absolutely huge construction,
0:31:34 > 0:31:37it's 8km long on its north and south sides,
0:31:37 > 0:31:40and 2km long on its east and west sides.
0:31:40 > 0:31:43It's an incredibly impressive piece of engineering.
0:31:53 > 0:31:59The West Baray is the largest hand-dug reservoir on the planet.
0:31:59 > 0:32:03It can hold over 48 million cubic metres of water.
0:32:03 > 0:32:07It's estimated that 200,000 people
0:32:07 > 0:32:10were needed to construct its high embankments.
0:32:17 > 0:32:21It's really remarkable to stand on the edge of the West Baray.
0:32:21 > 0:32:24It's just an enormous, beautiful lake
0:32:24 > 0:32:27built to precision engineering standards.
0:32:27 > 0:32:31But it's not just a functional piece of infrastructure,
0:32:31 > 0:32:34it's also really humbling and moving how beautiful it is.
0:32:37 > 0:32:41900 years after the baray was completed,
0:32:41 > 0:32:47its waters are still used to irrigate the surrounding fields during the dry season.
0:32:47 > 0:32:54The West Baray is really the pinnacle of the Khmers' ability to transform their environments
0:32:54 > 0:32:58and attempt to neutralise the flux of the monsoon.
0:32:59 > 0:33:03If you look at society today, we're all about risk management, climate change.
0:33:03 > 0:33:05They were doing the same thing back then,
0:33:05 > 0:33:10trying to manage these droughts and to even out the disturbances,
0:33:10 > 0:33:13so that the local population wouldn't revolt
0:33:13 > 0:33:16and the kings could manage their society.
0:33:16 > 0:33:21LIDAR work across Angkor shows how the Khmer people
0:33:21 > 0:33:25transformed this area with advanced hydraulic engineering.
0:33:30 > 0:33:33The elaborate network of canals and reservoirs
0:33:33 > 0:33:39meant that they could now grow crops far away from the area irrigated naturally by Tonle Sap.
0:33:41 > 0:33:44From an engineering point of view, what was achieved here is absolutely incredible.
0:33:44 > 0:33:50They moved phenomenal amounts of the landscape from different parts of Angkor to other areas
0:33:50 > 0:33:55and, basically, terraformed the entire plane into a completely artificial landscape
0:33:55 > 0:34:00in order to release themselves from these limitations
0:34:00 > 0:34:03of relying on the rainfall for one crop of rice per year.
0:34:07 > 0:34:10A Chinese diplomat writing in the 13th century
0:34:10 > 0:34:17marvelled at the Khmers' ability to harvest three or even four crops a year from their irrigated lands.
0:34:18 > 0:34:23Once you've solved the problem of water supply, you've solved the problem of food security.
0:34:23 > 0:34:28What you've done then is provided an extremely solid economic foundation for the growth of the empire.
0:34:29 > 0:34:33The king can turn his attention to things like empire-building,
0:34:33 > 0:34:35to warfare, to temple-building and so on,
0:34:35 > 0:34:41and so it's a complete transformation, actually, in the way that things are done in Cambodia.
0:34:42 > 0:34:45This mastery of the natural environment is one of the reasons
0:34:45 > 0:34:49for the rise and the success of the Khmer Empire.
0:34:53 > 0:34:55These engineering projects
0:34:55 > 0:34:59demanded huge investments of labour and expertise.
0:34:59 > 0:35:03The whole society had to contribute time and resources
0:35:03 > 0:35:06to build the system of canals and reservoirs.
0:35:09 > 0:35:1310km from Angkor Wat is Preah Ko temple.
0:35:16 > 0:35:19Inscriptions on the walls of this 9th-century shrine
0:35:19 > 0:35:21tell how the Angkorian kings
0:35:21 > 0:35:24used the temple system to tax the population.
0:35:26 > 0:35:30Archaeologist Julia Esteve has spent the last ten years translating them.
0:35:31 > 0:35:35Most people think that temples are only religious entities,
0:35:35 > 0:35:38but you have to understand the king, Jayavarman II,
0:35:38 > 0:35:41the founder of the Khmer Empire
0:35:41 > 0:35:43was at the same time a god
0:35:43 > 0:35:48and used the temples to strengthen his economic and political power,
0:35:48 > 0:35:51and so these temples are not only religious entities,
0:35:51 > 0:35:55but also economical and political tools.
0:35:56 > 0:36:00Temples had administrative as well as religious functions.
0:36:02 > 0:36:04No coins have been found from this period,
0:36:04 > 0:36:08it's thought the economy was run by exchange and barter,
0:36:08 > 0:36:11with a duty to make donations to the temples.
0:36:11 > 0:36:16There were contributions coming from the lower strata of the society made by rice farmers.
0:36:16 > 0:36:19They would donate some of their time to the temple
0:36:19 > 0:36:22in order to give some rice to the god.
0:36:22 > 0:36:26With these kind of donations, we see another side of the temples,
0:36:26 > 0:36:31and through the temples, the king would develop a system of taxation.
0:36:44 > 0:36:46Inscriptions from the temple walls
0:36:46 > 0:36:50suggest that payments took a surprising variety of forms.
0:36:52 > 0:36:54This is one of the inscriptions.
0:36:54 > 0:36:59And it's a fascinating text because it gives us the list of goods
0:36:59 > 0:37:02donated to this particular shrine.
0:37:02 > 0:37:07We have, for example, an umbrella-holder, a spice-grinder.
0:37:07 > 0:37:09Also a garland-maker.
0:37:09 > 0:37:13And along with this, we also have workers that would give labour.
0:37:13 > 0:37:16But Julia's work has revealed
0:37:16 > 0:37:19that people would also give up their own children.
0:37:20 > 0:37:24We can see children. There is here a baby.
0:37:24 > 0:37:28And over here there is a child who is at the age of running.
0:37:28 > 0:37:33So children were donated to a temple or were considered as future workers
0:37:33 > 0:37:37to help all the people who were here to serve the gods.
0:37:37 > 0:37:43The inscriptions reveal a highly hierarchical society built on forced labour.
0:37:43 > 0:37:47Julia's studies show how the Angkorian kings
0:37:47 > 0:37:52built a network of religious shrines to consolidate their imperial power.
0:37:54 > 0:37:58And LIDAR reveals the footprint of these religious buildings
0:37:58 > 0:38:00across the medieval city.
0:38:00 > 0:38:04LIDAR isn't just useful for areas that are covered by forest,
0:38:04 > 0:38:08we also flew the instrument over large areas of open landscape.
0:38:08 > 0:38:14And even in those areas, we're getting tremendous new insights into archaeological sites
0:38:14 > 0:38:17that lie out in the open rice fields.
0:38:17 > 0:38:21There are some things that just jump out of the imagery at you.
0:38:21 > 0:38:23There are some classes of temples
0:38:23 > 0:38:25that have a very, very distinctive layout.
0:38:30 > 0:38:355km from Angkor Wat, close to the edge of another huge reservoir,
0:38:35 > 0:38:37the ghostly footprint of one of these buildings
0:38:37 > 0:38:40appears on the LIDAR map.
0:38:40 > 0:38:45300 metres in length and clearly broken into three sections,
0:38:45 > 0:38:48these were "ashramas",
0:38:48 > 0:38:52part monastery, part tax office, part school.
0:38:52 > 0:38:54The building behind me is an ashrama,
0:38:54 > 0:38:59and we know that there were communities of religious people living in the ashramas,
0:38:59 > 0:39:03but we also think that some people, if they could afford it,
0:39:03 > 0:39:06could send their kids to get educated,
0:39:06 > 0:39:09maybe...to learn how to read.
0:39:17 > 0:39:21These ashramas reveal the growing sophistication of Angkor.
0:39:21 > 0:39:23Some were now wealthy enough
0:39:23 > 0:39:26to invest their time in leisure and learning,
0:39:26 > 0:39:31and their religious buildings were taking on a grander scale.
0:39:31 > 0:39:34We're able now to say that they all had the same layout,
0:39:34 > 0:39:36for those in Angkor at least.
0:39:36 > 0:39:40And they were built around a central sacred building
0:39:40 > 0:39:43where the religious people would gather.
0:39:48 > 0:39:52Many ashramas were built on the edges of Angkorian territory,
0:39:52 > 0:39:55a symbol of Khmer power
0:39:55 > 0:39:59and a demonstration that the land around
0:39:59 > 0:40:02belonged to a strong and unified empire.
0:40:02 > 0:40:05We know from writings from the time
0:40:05 > 0:40:10that the king needed money and a lot of people to build ashramas.
0:40:10 > 0:40:14The building of more than 100 came at a period of great economic growth.
0:40:16 > 0:40:19The king who built these ashramas all over the country
0:40:19 > 0:40:21wanted to put his stamp on these lands
0:40:21 > 0:40:25by saying, "This is my kingdom. I'm a strong king.
0:40:25 > 0:40:28"I'm the best of the kings. I'm the king of the kings.
0:40:28 > 0:40:30"And now these lands are mine."
0:40:30 > 0:40:33By the end of the 11th century,
0:40:33 > 0:40:37Khmer lands stretched across the modern-day borders of Vietnam,
0:40:37 > 0:40:39Laos and Cambodia.
0:40:39 > 0:40:43The Khmer Empire now dominated the region.
0:40:46 > 0:40:51Mitch Hendrickson, an archaeologist from the University of Illinois,
0:40:51 > 0:40:56has been studying how the Khmer expanded beyond today's borders of Cambodia.
0:40:57 > 0:41:01We're actually following along the northwest road, which connects Angkor
0:41:01 > 0:41:05to the site of Phimai, which is in modern-day Thailand.
0:41:05 > 0:41:08The road extends roughly 280km,
0:41:08 > 0:41:13so we're really following in the footsteps of people from 1,000 years ago.
0:41:13 > 0:41:19The Khmer were the only people who built roads in Southeast Asia at this time.
0:41:21 > 0:41:27By the 11th century, they'd built 1,000km of roads across the region,
0:41:27 > 0:41:32a network that stretched to every part of their growing empire.
0:41:32 > 0:41:35The ultimate result of this road network
0:41:35 > 0:41:38is that it enabled the Khmer to become a regional superpower,
0:41:38 > 0:41:41enabling them to branch off into different parts of Southeast Asia
0:41:41 > 0:41:46and led to their ultimate control over mainland Southeast Asia for about 200 years.
0:41:53 > 0:41:55Ox-drawn carts were used
0:41:55 > 0:41:59to carry copper, iron and food to the capital.
0:41:59 > 0:42:05As the empire expanded, trade improved the quality of life for the people of Angkor.
0:42:05 > 0:42:10Today's travellers would have recognised some of the roadside developments.
0:42:13 > 0:42:1740km from the capital - a medieval rest stop,
0:42:17 > 0:42:21part temple, part restaurant, part refuge.
0:42:21 > 0:42:26This is an excellent example of the type of infrastructure
0:42:26 > 0:42:32and the desire to create support for travellers moving in and out of Angkor,
0:42:32 > 0:42:34traders, pilgrims.
0:42:34 > 0:42:37There would have been many people who would have stayed here,
0:42:37 > 0:42:39seeking shelter from bandits
0:42:39 > 0:42:42or just to get some water from one of the nearby ponds.
0:42:46 > 0:42:50Along this road alone there are 17 rest areas
0:42:50 > 0:42:54each spaced a day's walk - about 20km - apart.
0:42:54 > 0:42:58Today, there's also an international frontier.
0:42:58 > 0:43:03So here we are at the modern-day border between Cambodia and Thailand.
0:43:03 > 0:43:06Of course, 1,000 years ago, during the peak of the Khmer Empire,
0:43:06 > 0:43:10Angkor's influence actually extended into this region.
0:43:11 > 0:43:12If I can find my passport...
0:43:17 > 0:43:20Imperial expansion into new territories
0:43:20 > 0:43:23also brought conflict and rebellion,
0:43:23 > 0:43:28and Khmer kings were capable of mustering huge armies.
0:43:30 > 0:43:34Carvings at Angkor Wat show a Khmer army on the march.
0:43:36 > 0:43:41Thousands of soldiers able to travel fast to wherever trouble flared.
0:43:43 > 0:43:48We're actually off to a temple now that commemorates the actions of one of the local lords
0:43:48 > 0:43:51who helped put down a rebellion for one of the Khmer kings.
0:44:01 > 0:44:04We're here at Phnom Rung...
0:44:04 > 0:44:09one of the most impressive temples on the edge of the Khmer Empire.
0:44:09 > 0:44:11Deep in enemy territory,
0:44:11 > 0:44:17this temple was extended to mark a Khmer leader's victory over a local rebellion.
0:44:22 > 0:44:25The large proportion of this temple that we see today
0:44:25 > 0:44:30was actually an embellishment that was made in honour of that particular lord.
0:44:30 > 0:44:33So we have this interwoven connection
0:44:33 > 0:44:37between the civil conflict and external expansion,
0:44:37 > 0:44:40which is interconnected with these road systems.
0:44:46 > 0:44:49Beyond Phnom Rung temple
0:44:49 > 0:44:53the road continues through what is now northeast Thailand.
0:44:54 > 0:44:57The northwest road that we're tracking right now
0:44:57 > 0:45:01is a little bit different from all the other of the Angkorian roadways
0:45:01 > 0:45:05which brought what we think are more precious commodities such as metals.
0:45:05 > 0:45:11The principal cargo passing along this road was a vital commodity.
0:45:11 > 0:45:16The Khmer's great northwest road leads to a giant open mine.
0:45:18 > 0:45:20It's still in use today.
0:45:28 > 0:45:31This is one of the reasons why the Khmer travelled
0:45:31 > 0:45:34hundreds of kilometres away from Angkor.
0:45:36 > 0:45:38Salt.
0:45:41 > 0:45:45What we're standing on now is a salt plain that we think was
0:45:45 > 0:45:48probably used back to about 500 BC, during the Iron Age.
0:45:50 > 0:45:54The salt would have been extremely important for so many reasons.
0:45:54 > 0:45:57We know that without salt the human body can't survive,
0:45:57 > 0:46:00and rice is one of the least saline of the cereal crops.
0:46:00 > 0:46:03It was very significant from a physiological perspective
0:46:03 > 0:46:06but, more significantly, we know that salt tastes good.
0:46:06 > 0:46:09So from the peasants to the elite
0:46:09 > 0:46:12and even the king, they would have desired this salt.
0:46:15 > 0:46:19Then, as now, salt was an important preservative.
0:46:21 > 0:46:25For a good chunk of the year you can get fresh fish, but in the rest
0:46:25 > 0:46:28of the year you need to maintain your source of protein, and the way
0:46:28 > 0:46:30that the Cambodians did it was
0:46:30 > 0:46:33to create this lovely dish called prahok.
0:46:33 > 0:46:36And prahok is essentially the salt from here,
0:46:36 > 0:46:41taken down there to ferment this lovely and extremely appetising
0:46:41 > 0:46:43fishy paste
0:46:43 > 0:46:48that doesn't look good but I'm going to give it a little taste,
0:46:48 > 0:46:50just to see how it goes, so let's try and find a bit.
0:46:50 > 0:46:52Give it a whirl.
0:46:55 > 0:46:57Whoof!
0:46:57 > 0:46:58Ho!
0:47:04 > 0:47:06Aw, man!
0:47:13 > 0:47:16By the late 12th century, 300 years after
0:47:16 > 0:47:19Jayavarman united the kingdom,
0:47:19 > 0:47:25the Khmer had built the biggest empire ever seen in Southeast Asia,
0:47:25 > 0:47:31and then a new king came to the throne, Suryavarman II.
0:47:34 > 0:47:37His story is one of the best-known in Khmer history,
0:47:37 > 0:47:42partly because of the reliefs carved into the walls of Angkor Wat.
0:47:42 > 0:47:46Here we have Suryavarman II in all his glory,
0:47:46 > 0:47:51probably the first time a Khmer king had been depicted in life.
0:47:51 > 0:47:54He's surrounded here by his court.
0:47:54 > 0:47:59We have the nobles, the Brahmin advisors,
0:47:59 > 0:48:01and all around there's a scene which takes place in a forest.
0:48:01 > 0:48:05There are animals cavorting around.
0:48:05 > 0:48:08There are processions of people. Women carried in palanquins.
0:48:08 > 0:48:13Soldiers... A scene of utter prosperity.
0:48:16 > 0:48:18It looks fantastic, it's beautiful.
0:48:26 > 0:48:30But this peaceful scene contrasts with the legend of how
0:48:30 > 0:48:34Suryavarman II became king.
0:48:34 > 0:48:38It's said that he stole the throne by raising an army against his
0:48:38 > 0:48:43aged uncle, the Khmer king, and killing him with his own hands.
0:48:47 > 0:48:51This section of Suryavarman's army has a quite a unique
0:48:51 > 0:48:56body of men, and they're wearing very distinct uniforms.
0:48:56 > 0:49:00An inscription actually identified them as being Siamese.
0:49:00 > 0:49:05So this is one of the first depictions of the Thai people.
0:49:05 > 0:49:08What it actually shows us is that Suryavarman was drawing
0:49:08 > 0:49:13mercenaries from the extent of his empire to fight for him.
0:49:18 > 0:49:21After the battle, Suryavarman brought his men back to
0:49:21 > 0:49:27Angkor to work on the most important building project of his reign,
0:49:27 > 0:49:31the biggest religious monument the world has ever seen.
0:49:31 > 0:49:34It would draw on everything the Khmer people had
0:49:34 > 0:49:37learned about architecture and temple-building.
0:49:39 > 0:49:44Former UNESCO regional advisor Richard Engelhardt has spent
0:49:44 > 0:49:46decades studying Angkor Wat.
0:49:53 > 0:49:58Once he became the king, Suryavarman II imposed a great
0:49:58 > 0:50:01peace over the entire empire,
0:50:01 > 0:50:05so he built this temple as a way of saying, "This is
0:50:05 > 0:50:11"the stability that I wish to impose upon our land,
0:50:11 > 0:50:15"and this stability is going to continue and continue for ever."
0:50:15 > 0:50:20It's the real pinnacle of the achievement of Khmer art.
0:50:22 > 0:50:26Suryavarman wanted his Angkor Wat to eclipse everything that had
0:50:26 > 0:50:28gone before.
0:50:28 > 0:50:31We have to remember that this is a temple to the god,
0:50:31 > 0:50:34and the god needs a universe populated with
0:50:34 > 0:50:37beautiful things, with beautiful women, beautiful goddesses,
0:50:37 > 0:50:40beautiful animals, and so they needed a
0:50:40 > 0:50:44vast canvas on which to sculpt all of these magical creatures.
0:50:44 > 0:50:47They did this by bringing these huge blocks of sandstone
0:50:47 > 0:50:50here on site, fitting them together almost flawlessly.
0:50:50 > 0:50:54There is no mortar, there's no mortar anywhere at Angkor.
0:50:54 > 0:50:57They fit the blocks together very, very precisely.
0:50:57 > 0:51:00Look, here's the sandstone blocks.
0:51:00 > 0:51:01You can almost not see the join,
0:51:01 > 0:51:04you certainly cannot even put your fingernail between it.
0:51:04 > 0:51:08All the technical expertise and wealth of the empire was
0:51:08 > 0:51:11channelled into this spectacular building.
0:51:14 > 0:51:17Most striking of all was the scale of the construction.
0:51:18 > 0:51:21Angkor Wat covers an area more than
0:51:21 > 0:51:24four times larger than the Vatican City.
0:51:26 > 0:51:32And this created huge challenges for Suryavarman's engineers.
0:51:32 > 0:51:35During the monsoon, the land becomes saturated
0:51:35 > 0:51:38and expands.
0:51:38 > 0:51:42After the monsoon, it dries out and contracts.
0:51:44 > 0:51:48How do you build high with such heavy material as this sandstone?
0:51:48 > 0:51:52Well, look behind the facade and what do you see?
0:51:52 > 0:51:55You see that it's filled with this very lightweight, porous
0:51:55 > 0:51:57material called laterite.
0:51:57 > 0:52:00It's a kind of ancient breeze block.
0:52:02 > 0:52:06Laterite was a core building material of all Khmer temples,
0:52:06 > 0:52:10stretching right back to the Kulen Hills.
0:52:11 > 0:52:15Now it was used to help solve the Khmer's greatest engineering
0:52:15 > 0:52:16challenge.
0:52:16 > 0:52:18This building is much,
0:52:18 > 0:52:21much lighter than you might think it is. The weight of the building
0:52:21 > 0:52:25is not pushing, pushing down and pressing out on the earth,
0:52:25 > 0:52:29but instead is rising up and you can build and build
0:52:29 > 0:52:32and build almost as high as your imagination lets you build.
0:52:32 > 0:52:35But Richard Engelhardt thinks that the use of laterite was only
0:52:35 > 0:52:38part of the solution.
0:52:38 > 0:52:41He believes that Angkor Wat is still standing today
0:52:41 > 0:52:45because of the water surrounding the great temple.
0:52:45 > 0:52:48In the ideal Khmer structure, you cannot separate
0:52:48 > 0:52:50the building from the moat.
0:52:50 > 0:52:52They are inextricable.
0:52:52 > 0:52:55They are symbiotic and you cannot have one without the other,
0:52:55 > 0:52:58both in the terms of the design and the conception
0:52:58 > 0:53:01of what we are building and the civil engineering features of it.
0:53:01 > 0:53:05Now, the Khmer were great artists, they never did anything that wasn't
0:53:05 > 0:53:09beautiful, but the real purpose of the moat is not for decoration.
0:53:11 > 0:53:14The construction of the moat surrounding Angkor Wat was
0:53:14 > 0:53:20a huge operation. It's estimated labourers removed enough silt
0:53:20 > 0:53:24and sand to fill St Paul's Cathedral ten times over.
0:53:26 > 0:53:33Its perimeter stretches nearly 6 kilometres and is 200 metres wide.
0:53:34 > 0:53:36Then the moat fills with water.
0:53:36 > 0:53:40Water is heavier, it's more dense than laterite and earth,
0:53:40 > 0:53:44so the weight of the water is actually heavier than
0:53:44 > 0:53:46the weight of the materials you've taken out.
0:53:49 > 0:53:52Richard believes the weight of the water in the moat pushes
0:53:52 > 0:53:55back against the downward force of the stone temple.
0:53:57 > 0:54:01The moat is essential to the success of the entire structure.
0:54:01 > 0:54:05Without the moat, the structure could not stand.
0:54:05 > 0:54:11The two are completely part of one holistic engineering system.
0:54:13 > 0:54:17The Khmer had become masters of the monsoon.
0:54:19 > 0:54:23Angkor Wat was an engineering masterpiece.
0:54:25 > 0:54:28Everything the Khmer had learned over hundreds of years
0:54:28 > 0:54:31of temple-building and engineering great water projects
0:54:31 > 0:54:36came together in the construction of the jewel of their civilisation.
0:54:37 > 0:54:40Through hundreds of years of experimentation
0:54:40 > 0:54:44and gradual augmentation, we find that moving from a very,
0:54:44 > 0:54:49very simple rice paddy to this extraordinary expression
0:54:49 > 0:54:55of both civil engineering genius and an ability to communicate
0:54:55 > 0:54:58through the symbolic meaning of Angkor,
0:54:58 > 0:55:03this is what is so extraordinary about this particular monument.
0:55:05 > 0:55:07Absolutely a stroke of genius.
0:55:08 > 0:55:11The LIDAR project is enhancing our understanding of
0:55:11 > 0:55:14the Angkorian empire and shedding new light on
0:55:14 > 0:55:17the great civilisation that built it.
0:55:17 > 0:55:21But it has also uncovered new mysteries.
0:55:22 > 0:55:26Even though LIDAR has in, in some senses, transformed our vision
0:55:26 > 0:55:30of Angkor by giving us new insights into the cities,
0:55:30 > 0:55:33there are a couple of things which really took us completely by surprise.
0:55:36 > 0:55:41Emerging from the LIDAR data by the side of Angkor Wat's moat,
0:55:41 > 0:55:44the outline of eight huge coiled shapes,
0:55:44 > 0:55:47partly obscured by the remains of a canal,
0:55:47 > 0:55:52each one more than 700 metres in length.
0:55:52 > 0:55:55Nothing like them has ever been seen before.
0:55:57 > 0:56:00In terms of the features that we can see in the LIDAR,
0:56:00 > 0:56:03those are definitely the most striking.
0:56:03 > 0:56:05You wouldn't know it just to look down there,
0:56:05 > 0:56:09you basically can't see anything from above except forest
0:56:09 > 0:56:11right next to the moat of Angkor Wat right there.
0:56:16 > 0:56:19These shapes have remained hidden for hundreds of years,
0:56:19 > 0:56:24right next to one of the area's busiest roads.
0:56:24 > 0:56:26We've launched a campaign of excavation
0:56:26 > 0:56:28and closer study onto these features
0:56:28 > 0:56:31to try and really come to terms with what they might be.
0:56:31 > 0:56:34A team of Cambodian archaeologists is excavating
0:56:34 > 0:56:39a section of one of these coils. They're looking for any physical
0:56:39 > 0:56:44evidence - tools or pottery - that might suggest why they were built.
0:56:44 > 0:56:47Some people have speculated that they're gardens,
0:56:47 > 0:56:50that they're used for agriculture,
0:56:50 > 0:56:54perhaps that they have some sort of ritual or symbolic dimension.
0:56:54 > 0:56:59All the excavations so far have proved inconclusive.
0:56:59 > 0:57:03No clues about their meaning or function have been found.
0:57:03 > 0:57:06It's the nature of the game that there's not much
0:57:06 > 0:57:08certainty here.
0:57:08 > 0:57:10We might never understand fully what these things are.
0:57:10 > 0:57:13And I guess, as archaeologists, sometimes we just have to
0:57:13 > 0:57:15resign ourselves to that reality.
0:57:19 > 0:57:23Angkor Wat marked the high point of the Khmer's artistic,
0:57:23 > 0:57:26architectural and engineering skill.
0:57:29 > 0:57:32It's a great symbol of a civilisation that grew from
0:57:32 > 0:57:36the rice paddies of the Kulen Hills and came to dominate the region.
0:57:39 > 0:57:42Angkor Wat is a peak of Khmer society.
0:57:42 > 0:57:45It was a statement of where they'd come from
0:57:45 > 0:57:47and where they were heading to.
0:57:47 > 0:57:49LIDAR is revealing the epic scale
0:57:49 > 0:57:52and sophistication of the Khmer capital
0:57:52 > 0:57:56and helps to explain how the Khmer people
0:57:56 > 0:58:00transformed their landscape and turned rice into gold.
0:58:00 > 0:58:05Angkor is totally unique, and the things that were achieved here were
0:58:05 > 0:58:10unparalleled throughout all of human history.
0:58:10 > 0:58:15In the next programme, a vast new temple-building project,
0:58:15 > 0:58:21the Khmer Empire's great metropolis faces destruction
0:58:21 > 0:58:24and LIDAR helps explain why the Khmer people
0:58:24 > 0:58:27allowed their capital to be devoured by the jungle.